Tag: optical telescope

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Questions Related to optical telescope

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

In the spectrum of light from a star, the wavelength of a particular line is measured to be $4747 $, while the actual wavelength of the line is $4700 $. What is the relative velocity ?

  1. $2\times10^5 m/s$
  2. $3\times10^5 m/s$
  3. $3\times10^6 m/s$
  4. $4.5\times10^6 m/s$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using the Doppler effect formula for light, delta_lambda / lambda = v / c, where delta_lambda = 4747 - 4700 = 47. Assuming typical values or a misprint in the prompt numbers where delta_lambda is 47 and lambda is 4700, v = c * (delta_lambda / lambda) = (3 x 10^8) * (47 / 4700) = 3 x 10^6 m/s.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

The objective of a telescope A has diameter 3 times that of the objective of telescope B, How much greater amount of light is gathered by A as compared to B?

  1. $\dfrac { 1 }{ 9 } $
  2. $\dfrac { 1 }{ 3 } $

  3. 3

  4. 9
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The amount of light gathered by a telescope objective is proportional to its area, which scales with the square of its diameter (A proportional to D^2). Since the diameter of telescope A is 3 times that of telescope B, the light gathering power is 3^2 = 9 times greater.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

For an electron microscope, which of the following is false ?

  1. It uses magnetic lens to converge electron beam.

  2. Its resolving power is directly proportional to accelerating potential of electron.

  3. Its resolving power is inversely proportional to wavelength of electrons
  4. Magnification attained with the help of of it of the order of $10^6$.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For an electron microscope: (A) is correct - magnetic lenses are used to focus the electron beam. (C) is correct - resolving power is inversely proportional to electron wavelength (R ∝ 1/λ). (D) is correct - electron microscopes can achieve magnifications of ~10⁶. (B) is FALSE - resolving power is NOT directly proportional to accelerating potential; it increases with potential because higher potential reduces electron wavelength (λ = h/√(2meV)), but this is an inverse relationship, not direct proportionality.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

 If an object subtend angle of $2^o$ at eye when seen through telescope having objective and eyepiece of focal length $f = 60\, cm $and $f = 5\, cm$ respectively than angle subtend by image at eye piece will be 

  1. $16^o$
  2. $50^o$
  3. $10^o$
  4. $24^o$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The magnifying power of a telescope in normal adjustment is given by m = f_o / f_e = 60 / 5 = 12. The angle subtended by the image at the eyepiece is equal to the magnification times the angle subtended by the object at the objective, so beta = m * alpha = 12 * 2 degrees = 24 degrees.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

A telescope has an objective of focal length $50 cm$ and an eye-piece of focal length $5 m$ THe least distance of distinct vision is $25 cm$. The telescope is focused for distinct vission a scale $200 cm$ away from the objective.The separation between the two lenses is nearly 

  1. $71 cm$
  2. $61 cm$
  3. $81 cm$
  4. $51 cm$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

Match the items given in A, B, C and D against their corresponding description given in 1, 2, 3, 4 and 5.
A. Astronomical telescope
B. Galilean Telescope
C. Simple Microscope
D. Compound Microscope

1. Contains one convex lens
2. Contains one concave lens
3. Contains a convex lens of large focal length in the objective and a convex lens of small focal length in the eye-piece
4. Contains a convex lens of small focal length in the objective and a convex lens of large focal length in the eye-piece
5. Contains a convex lens of large focal length in the objective and a concave lens of small focal length in the eye-piece. 

  1. $2\, \quad\, 3\, \quad\, 1\, \quad\, 5$
  2. $3\, \quad\, 2\, \quad\, 4\, \quad\, 1$
  3. $2\, \quad\, 5\, \quad\, 3\, \quad\, 4$
  4. $3\, \quad\, 5\, \quad\, 1\, \quad\, 4$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A). Astronomical telescope - Contains a convex lens of large focal length in the objective and a convex lens of small focal length in the eye-piece

B.) Galilean Telescope - Contains a convex lens of large focal length in the objective and a concave lens of small focal length in the eye-piece
C). Simple Microscope - Contains one convex lens
D.) Compound Microscope - Contains a convex lens of small focal length in the objective and a convex lens of large focal length in the eye-piece
Thus,
A  -  3 , B  -  5 , C  -  1 and D  -  4 , hence Option D is correct.

Multiple choice physics observing space: telescopes optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

The sum of the focal lengths of the objective and an eyepiece, In case of an astronomical telescope is equal to : ( final image is at $\infty$)

  1. The length of the telescope

  2. Half the length of the telescope

  3. Double the length of the telescope

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

The astronomical telescope makes use of two positive lenses: the objective, which forms the image of a distant object at its focal length, and the eyepiece, which acts as a simple magnifier with which to view the image formed by the objective. Its length is equal to the sum of the focal lengths of the objective and eyepiece, and its angular magnification is -fo/fe , giving an inverted image.
Hence, the sum of the focal lengths of the objective and an eyepiece, In case of an astronomical telescope is equal to the length of the telescope.

Multiple choice physics option c: imaging optical instruments : telescope the reflecting telescope optical telescope xx radio telescope and space telescopes

The focal lengths of the objective and the eyepiece of an astronomical telescope are 20 cm and 5 cm respectively. If the final image is formed at a distance of 30 cm from the eyepiece, find the separation between the lenses required for distinct vision

  1. 32.4 cm

  2. 42.3 cm

  3. 24.3 cm

  4. 30.24 cm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

$f _{0}=20cm$


$f _{e}=5cm$

$V _{e}=30cm = D$

$L=?$

$L _{D}=f _{0}+ \dfrac{Df _e}{D+f _e}$ $=20+\dfrac{5\times 30}{35}=24.3 cm$